Typically, bipedal robots like Agile Technologies’ Cassie need plenty of processing power to run the balancing algorithms, gyroscopes and sensors to keep it on its feet. However, with the PER, it uses an elegant mechanical design, with a single motor that drives the legs in an elliptical motion. The body’s shape adds to its stability and the design means that the robot’s legs have “reactive resilience”: when the legs feel resistance, it adds more power to push through, as well as mechanically adjusting the rear leg to stabilise its sprint. If the robot was scaled up to human size, the speed could reach between 20 or 30 mph.
Biped robots are typically harder to balance, more power-hungry and more expensive, but as they can dynamically balance, like Boston Dynamics humanoid offerings, they can get to places other robots can’t. “Robots with legs will be particularly useful in places where you want a human presence, but it’s too dangerous, expensive, or remote to send a real human,” Pratt told Technology Review.
